Prior to the present invention a variety of homogeneous and heterogeneous catalysts have been reported in the literature for oxidation of various organic compounds including tetralin with gaseous oxygen. Many of the known catalyst systems have various problems with respect to reactant conversion, product yield, catalyst and product recovery, and the like, which have prevented many of these processes from becoming commercially successful.
One such reaction involves the oxidation of 1,2,3,4-tetrahydronaphthalene to 1(2H)naphthalenone, which is commonly referred to as "1-tetralone". Sizeable amounts of 1-tetralone are produced in the United States each year for use as an intermediate in the manufacture of insecticides as well as in the manufacture of other agricultural chemicals and drugs. Typically, 1-tetralone has been prepared by the liquid phase oxidation of tetralin in the presence of a homogeneous oxidation catalyst, with and without catalyst modifiers to improve reaction selectivity to 1-tetralone.
A fundamental problem with these homogeneous oxidation catalyst processes has been the relative difficulty in isolating the desired 1-tetralone or other products from the reaction mixture, regardless of selectivity. Not only must the undesired reaction by-products be separated from the desired product, but the homogeneous oxidation catalyst and homogeneous catalyst modifiers, if used, also must be separated out and recovered for subsequent reuse. As a result, the isolation of desired product, such as 1-tetralone, has historically required additional time-consuming distillation and other processing procedures thereby increasing production and other costs.
It is also known to use heterogeneous oxidation catalyst systems for the production of a 1-tetralone from tetralin. However, in many of these catalyst systems the selectivity of 1-tetralone is poor. Also, some of these catalysts are fine powders which can lead to plugging problems in the reactor. Good agitation is needed for the catalyst to be available in the entire reaction zone and hence, packed beds are not very suitable for the gas-liquid reactions. Also, some of these processes use homogeneous catalyst modifiers which require multi-step separation still involving difficult and costly distillation procedures to remove the homogeneous modifier.
In contrast, most of the difficulties and disadvantages of the known methods have been overcome by the present invention. The novel insoluble catalyst compositions and process for using same, as disclosed herein, solve these fundamental problems found in prior art whole-or part-homogeneous catalyst systems for the oxidation of tetralin. The instant catalysts provide considerable advantages over the multi-part catalyst and modifier combinations. The need for a separate homogeneous modifier and the attendant additional processing and recovery steps are eliminated.
Accordingly, an object of this invention is to provide an improved liquid-phase process for the oxidation of tetralin to tetralone.
Another object of this invention is to provide an improved process for oxidation of tetralin in the presence of an insoluble catalyst.
A further object is to provide an improved process for the oxidation of tetralin which achieves high conversion rates and thereby permitting the use of a small continuous oxidation reaction zone.
Another object of this invention is to provide a process for the oxidation of tetralin wherein substantially no waste or by-product streams are produced.
Other objects, aspects, as well as the several advantages of the invention will be apparent to those skilled in the art upon reading the specification and appended claims.